This research focuses on basic neural and cognitive processes related to the acquisition and retrieval of information from human memory. Specifically, subjects are required to form different types of associations between pairs of words or pairs of pictures of objects. Later, they are presented with these same stimuli plus stimuli not seen earlier, and, for each of these stimuli, are asked to judge whether the test stimulus had been presented earlier. In different experiments, these test stimuli may be individual words or pictures pairs of words/pictures in the original order, pairs of words/pictures in different orders, etc. During the encoding and test phases, the electrical activity of subjects' brains will be measured by the event-related potential (ERP) technique using an array of 128 electrodes. This wil yield a detailed millisecond by millisecond record of the brain's activity while forming associations and retrieving the resulting information from memory. IN addition, the dense electrode array will yield detailed spatial/topographic information about the areas of the brain that are involved. This temporal and spatial ERP evidence will then be combined with structural information about each subject's head obtained from an MRI scan using a new approach to ERP source localization whereby the MRI image is used to construct a mathematical model of the subject's head. This model is then used to guide a non-linear estimaiton procedure which searches for the best-fitting configuration of ERP sources in the brain. These sources are then plotted on the MRI. This approach should make it possible to localize brain signals corresponding to the formation/encoding of associations and the subsequent memory retrieval of individual items and associations between these items. This research is of importance not only for its value as basic research into the cognitive neuroscience of memory, but also for the insights it is likely to yield into memory disorders involved in aging and forms of amnesia resulting from temporal-lobe and thelamic brain damage. This follows because the elderly frequently have difficulty in "binding" or associating in memory different aspects of a situation, while amnesics frequently indiscriminately over-associate.